I can understand the problem here. Supervisor just goes on sending the Email every hour unless we do something about the Ticket and move it to some other status or value.Currently we don't have the frequency option but we can surely prevent these continuous emails.
Let me help, How this can be addressed.
We ourselves have a Supervisor rule in Freshdesk - Escalation - Which is designed to send myself/Product Manager/CEO an Email, whenever a Ticket crosses more than 4 Agent Iteration.
We have a Custom Dropdown - Escalation Sent with YES/NO options and in all our Dispatch'r rule, we add the Action - Escalation Sent - NO
So whenever a Ticket is created, automatically NO is set.
Now the Supervisor rule has the condition + Escalation Sent - NO, then Trigger the Actions + Escalation Sent - YES
Our Supervisor rule runs the Check on all the Tickets that are OPEN/PENDING/AWAITING CUSTOMER RESPONSE + Escalation Sent - NO and trigger the action as defined.
You can even push this further with Multiple Notifications like 1st Notification Sent , 2nd and so on.